Issue 31, 2018

Electrochemical water oxidation using a copper complex

Abstract

Herein, we report the application of the mononuclear copper complex 1, [CuII(L)]2+, in electrochemical water oxidation catalysis (L = 1,3-bis(((1-methyl-1H-imidazol-2-yl)methyl)amino)propan-2-ol). The complex exhibits a N4 donor set consisting of two amine and two imidazole units and a dangling OH unit in close proximity to the copper ion. 1 exhibits a moderate apparent rate constant kcat of 0.12 s−1 in catalysis and operates at an overpotential of 0.83 V. Detailed investigations allowed us to derive a mechanism for water oxidation. The catalysis proceeds only under basic conditions, where [CuII(L)(OH)]+, 1H−1, is the main solution species, which indicates that a negatively charged ligand is necessary to drive the catalysis. Initial oxidation of 1H−1 is coupled to proton loss forming a copper(III) species and further oxidation initiates oxygen evolution. Initial oxidation of 1 under neutral, i.e. non-catalytic, conditions is pH independent, highlighting the importance of PCET steps during catalysis. We collected reasonable evidence that catalysis proceeds via a water nucleophilic attack mechanism. The electrolyte presumably acts as a proton acceptor in catalysis as the onset potential depends on the buffer employed.

Graphical abstract: Electrochemical water oxidation using a copper complex

Supplementary files

Article information

Article type
Paper
Submitted
05 apr 2018
Accepted
07 jun 2018
First published
07 jun 2018
This article is Open Access
Creative Commons BY-NC license

Dalton Trans., 2018,47, 10737-10741

Electrochemical water oxidation using a copper complex

S. Nestke, E. Ronge and I. Siewert, Dalton Trans., 2018, 47, 10737 DOI: 10.1039/C8DT01323C

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